During heavy rain, a section of a mountainside measuring 5.4 km horizontally (perpendicular to the slope) 0.40 km up along the slope, and 2.8 m deep slips into a valley in a mud slide. Assume that the mud ends up uniformly distributed over a surface area of the valley measuring 1.2 km x 1.2 km and that the mass of a cubic meter of mud is 1900 kg. What is the mass of the mud sitting above a 1.8 m2 area of the valley floor?